Bacteriology Practice Questions

Q: Not true about meningococcal meningitis

Carriers are treated with penicillin. ***Carriers are treated with penicillin*** - **Penicillin** is not the recommended treatment for eradicating *Neisseria meningitidis* from carriers, as it does not reliably eliminate nasopharyngeal carriage. - Recommended prophylactic regimens for carriers include **rifampicin**, **ceftriaxone**, or **ciprofloxacin** [1]. *Transmitted via droplet infection* - **Meningococcal meningitis** is indeed highly contagious and primarily spreads through **respiratory droplets**, making close contact a significant risk factor. - This mode of transmission is why outbreaks can occur rapidly in crowded settings like dormitories or military barracks. *Is gram negative organism* - *Neisseria meningitidis*, the causative agent of meningococcal meningitis, is a **Gram-negative diplococcus**. - Its unique Gram stain morphology helps in initial laboratory identification. *Carriers are treated with Rifampicin.* - **Rifampicin** is a highly effective antibiotic for eliminating *Neisseria meningitidis* carriage in asymptomatic individuals and is commonly used for prophylaxis [1]. - Its mechanism allows it to penetrate host cells and target the bacteria in the nasopharynx. *Carriers are the source of infection* - **Asymptomatic carriers** of *Neisseria meningitidis*, who harbor the bacteria in their nasopharynx without developing disease, are the primary **reservoir and source of infection**. - These carriers facilitate the spread of the pathogen within communities, often unknowingly.

Q: Which is the most common organism causing acute epiglottitis among the following options?

H. influenzae. ***H. influenzae*** - **_Haemophilus influenzae_ type b (Hib)** was historically the **most common cause** of acute epiglottitis, particularly in children before widespread Hib vaccination. - This remains the **classically taught answer** in medical education and is still relevant in **unvaccinated populations** or areas with low vaccination coverage. - **Important note:** In the **post-vaccine era** with widespread Hib vaccination, the incidence has decreased by >95%, and other organisms (particularly _Streptococcus_ species) have become relatively more common, especially in adults. - However, H. influenzae remains the organism most associated with acute epiglottitis in traditional medical teaching. *N. meningitidis* - **_Neisseria meningitidis_** primarily causes **meningococcal meningitis** and **meningococcemia** (fulminant septicemia). - While it can cause various invasive infections, it is **not a common cause** of acute epiglottitis. - Characteristic features include petechial/purpuric rash in septicemia. *S. pyogenes* - **_Streptococcus pyogenes_** (Group A Streptococcus) is the leading cause of **acute bacterial pharyngitis** ("strep throat"). - It causes complications like **acute rheumatic fever** and **acute post-streptococcal glomerulonephritis**. - In the post-Hib vaccine era, it has emerged as an **increasingly common cause** of epiglottitis, especially in adults, but is still less classically associated than H. influenzae in traditional teaching. *S. pneumoniae* - **_Streptococcus pneumoniae_** is a major cause of **community-acquired pneumonia, acute otitis media, bacterial meningitis**, and **bacteremia**. - While it can cause **supraglottitis/epiglottitis** (particularly in adults in the modern era), it is **less classically associated** with acute epiglottitis compared to the traditional pathogen H. influenzae type b.

Q: Hebra nose is caused by:

Frisch bacillus. ***Frisch bacillus*** - **Frisch bacillus**, also known as *Klebsiella rhinoscleromatis*, is the causative agent of **rhinoscleroma**, which often presents as a condition causing tumor-like growths in the nose, leading to the characteristic "Hebra nose." - **Hebra nose** refers to the chronic, deforming nasal lesion associated with late stages of **rhinoscleroma**, characterized by hardening and widening of the nose. *C. diphtheriae* - *Corynebacterium diphtheriae* causes **diphtheria**, primarily affecting the respiratory tract and skin. - It forms a **pseudomembrane** in the throat and can lead to systemic complications due to toxin production, but it does not cause Hebra nose. *Pseudomonas* - *Pseudomonas aeruginosa* is an opportunistic pathogen commonly causing **nosocomial infections**, such as pneumonia, urinary tract infections, and wound infections. - While it can cause various infections, it is not associated with the specific nasal deformity known as Hebra nose. *Staph aureus* - *Staphylococcus aureus* is a common bacterium causing a wide range of infections, including **skin infections** (e.g., boils, cellulitis), **pneumonia**, and **sepsis**. - Although it can cause nasal colonization and local infections, it does not cause the chronic, deforming condition known as Hebra nose.

Q: Chancroid is caused by ?

H. ducreyi. ***H. ducreyi*** - **Chancroid** is a sexually transmitted infection characterized by painful genital ulcers and is specifically caused by the bacterium **Haemophilus ducreyi**. - This bacterium requires specialized culture media for isolation, contributing to diagnostic challenges. *N. Gonorrhoeae* - This bacterium is responsible for **gonorrhea**, a common STI causing urethritis, cervicitis, and other inflammatory conditions. - Unlike chancroid, gonorrhea typically presents with purulent discharge and can lead to complications like pelvic inflammatory disease, but not painful genital ulcers as the primary manifestation. *T. Pallidum* - This spirochete is the causative agent of **syphilis**, an STI that progresses through distinct stages. - Syphilis initially presents with a painless chancre, which is a key differentiator from the painful ulcers of chancroid. *H. influenzae* - **Haemophilus influenzae** is a common respiratory pathogen known to cause infections such as otitis media, epiglottitis, and pneumonia. - It is not associated with sexually transmitted infections or genital ulcers.

Q: Malignant pustules are seen in:

Anthrax. ***Anthrax*** - Cutaneous anthrax, caused by *Bacillus anthracis*, presents with a characteristic **painless ulcer with a black eschar** (malignant pustule) and surrounding edema. - This lesion evolves from a papule to a vesicle, then to a necrotic ulcer or "malignant pustule." *Pemphigus* - Pemphigus is an **autoimmune blistering disease** characterized by fragile blisters and erosions on the skin and mucous membranes. - It does not involve "malignant pustules" but rather flaccid bullae due to acantholysis. *Tularemia* - Tularemia, caused by *Francisella tularensis*, can present with an **ulceroglandular lesion** at the site of inoculation, but this is typically a single, painful ulcer with regional lymphadenopathy, not a "malignant pustule." - The ulcer is often clean-based and lacks the characteristic black eschar seen in anthrax. *Actinomycosis* - Actinomycosis is a bacterial infection caused by *Actinomyces species*, commonly presenting as **chronic, suppurative abscesses** that form sinus tracts. - The lesions are characterized by granulomas and "sulfur granules" in the pus, not "malignant pustules."

Q: A sexually active 25-year-old man develops epididymitis and orchitis. Needle biopsy demonstrates a prominent leukocytic infiltrate with numerous neutrophils. Which of the following organisms is the most likely cause of this man's infection?

Neisseria gonorrhoeae. ***Neisseria gonorrhoeae*** - In a sexually active man under 35, **Neisseria gonorrhoeae** is a common cause of epididymitis and orchitis, often manifesting with a prominent **neutrophilic infiltrate**. - This organism is a **Gram-negative diplococcus** that causes gonococcal urethritis, which can ascend to cause epididymitis. *Pseudomonas sp* - **Pseudomonas** infections of the genitourinary tract are typically associated with **nosocomial infections**, indwelling catheters, or compromised immune systems. - While it can cause severe inflammation, it is less common in a healthy, sexually active young man without predisposing factors. *Escherichia coli* - **E. coli** is a common cause of epididymitis, particularly in men over 35 or those engaging in **anal intercourse**, often due to retrograde flow of infected urine. - While it can cause an inflammatory response, *Neisseria gonorrhoeae* is more prevalent in the described demographic for sexually transmitted infections. *Mycobacterium tuberculosis* - **Mycobacterium tuberculosis** causes granulomatous inflammation and typically presents with **caseating necrosis** and **giant cells** rather than a prominent neutrophilic infiltrate. - While it can cause chronic epididymitis, it causes a different histological picture and is less acute than described.

Q: Which of the following is the most common cause of subacute endocarditis?

Streptococcus viridans. ***Streptococcus viridans*** - This group of bacteria is the most frequent cause of **subacute bacterial endocarditis**, particularly in individuals with pre-existing valvular heart disease. - They typically cause a **slowly progressive infection** on damaged heart valves, often following dental procedures. *Staphylococcus epidermidis* - This bacterium is a common cause of **nosocomial infections** and endocarditis associated with **prosthetic heart valves** or intravascular devices. - While it can cause endocarditis, it is less common than *S. viridans* for native valve subacute endocarditis. *Streptococcus pyogenes* - *S. pyogenes* is known for causing pharyngitis ("strep throat"), cellulitis, and **rheumatic fever**, which can lead to valvular damage. - However, it is a rare direct cause of infective endocarditis. *Staphylococcus aureus* - This bacterium is a common cause of **acute infective endocarditis**, particularly in intravenous drug users and those with prosthetic valves or catheters. - It typically causes a **rapidly destructive infection** and is less commonly associated with the subacute form.

Q: True statement about diphtheria toxin is -

Toxin is phage mediated. ***Toxin is phage mediated*** - The diphtheria toxin gene (tox gene) is carried by a **bacteriophage (a bacterial virus)**, specifically a lysogenic bacteriophage called corynephage beta. - This means that *Corynebacterium diphtheriae* only produces the toxin if it has been infected by and integrated the DNA of this specific bacteriophage into its genome, a process known as **lysogenic conversion**. *Toxin acts by inhibiting synthesis of capsule* - The diphtheria toxin specifically inhibits **protein synthesis** in eukaryotic cells by inactivating **Elongation Factor 2 (EF-2)**. - It does not interfere with the synthesis of a bacterial capsule, which *Corynebacterium diphtheriae* typically does not possess. *Endotoxaemia causes systemic manifestation* - Diphtheria toxin is an **exotoxin**, meaning it is secreted by the live bacterium and causes systemic effects by entering the bloodstream. - **Endotoxins** are components of the outer membrane of gram-negative bacteria (specifically **Lipopolysaccharide or LPS**) that are released upon bacterial cell lysis, and *Corynebacterium diphtheriae* is a gram-positive bacterium. *Toxin is required for local infection* - While the toxin is critical for the **virulence and systemic manifestations** of diphtheria, the initial local infection (e.g., pseudomembrane formation in the throat) is primarily due to bacterial growth and inflammatory response. - The toxin's main role is to cause **tissue necrosis** at the infection site and lead to serious systemic effects like **myocarditis** and **neuropathy**.

Q: Which of the following organisms is commonly implicated in spontaneous bacterial peritonitis in patients of Nephrotic syndrome?

Streptococcus pneumoniae. ***Streptococcus pneumoniae*** - This organism is a common cause of **spontaneous bacterial peritonitis (SBP)** in patients with **nephrotic syndrome**, particularly in children. - Patients with nephrotic syndrome are prone to infections due to impaired immunity (e.g., loss of immunoglobulins in urine) and **ascites**, providing a favorable environment for bacterial growth. *Salmonella* - While Salmonella can cause opportunistic infections, it is **not commonly implicated** in spontaneous bacterial peritonitis in nephrotic syndrome. - Salmonella typically causes **gastroenteritis** and can lead to bacteremia, but peritoneal infection is less common without direct bowel perforation. *Hemophilus influenza* - *Haemophilus influenzae* is a significant pathogen, but it is **not typically a cause** of spontaneous bacterial peritonitis in nephrotic syndrome. - It is more commonly associated with **respiratory infections**, meningitis, and epiglottitis. *Staphylococcus* - **Staphylococcal species** are generally not the primary cause of spontaneous bacterial peritonitis in uncomplicated nephrotic syndrome. - While *Staphylococcus aureus* can cause peritonitis, particularly in patients on **peritoneal dialysis** or with other predisposing factors, it is less common in SBP associated with nephrotic syndrome compared to *Streptococcus pneumoniae*.

Q: The most virulent pathogenic Bacillus species is

Bacillus anthracis. ***Bacillus anthracis*** - This species is the **causative agent of anthrax**, a severe and often fatal disease in humans and animals, making it the most virulent. - Its virulence is attributed to its **capsule** and the production of **anthrax toxins** (edema factor, lethal factor, and protective antigen). *Bacillus cereus* - Primarily known for causing **food poisoning** (emetic and diarrheal types) due to preformed toxins in contaminated food. - While it can cause opportunistic infections, it is generally considered **less virulent** than *B. anthracis*. *Bacillus subtilis* - This is a common **soil bacterium** and is often used as a **probiotic** and in industrial applications. - It is generally considered **non-pathogenic** to humans, though rare opportunistic infections have been reported in immunocompromised individuals. *Bacillus megaterium* - A large, **spore-forming bacterium** found in soil and various environments. - It is largely **non-pathogenic** and is commonly used in industrial microbiology for enzyme production.

Question 1

Not true about meningococcal meningitis

Accepted Answer

Carriers are treated with penicillin

Answer

Transmitted via droplet infection

Answer

Is gram negative organism

Answer

Carriers are treated with Rifampicin.

Answer

Carriers are the source of infection

Question 2

Which is the most common organism causing acute epiglottitis among the following options?

Accepted Answer

H. influenzae

Answer

N. Meningitidis

Answer

S. pyogenes

Answer

S. Pneumoniae

Question 3

Hebra nose is caused by:

Accepted Answer

Frisch bacillus

Answer

C. diphtheriae

Answer

Pseudomonas

Answer

Staph aureus

Question 4

Chancroid is caused by ?

Accepted Answer

H. ducreyi

Answer

N. Gonorrhoeae

Answer

T. Pallidum

Answer

H. influenzae

Question 5

Malignant pustules are seen in:

Accepted Answer

Anthrax

Answer

Pemphigus

Answer

Tularemia

Answer

Actinomycosis

Question 6

A sexually active 25-year-old man develops epididymitis and orchitis. Needle biopsy demonstrates a prominent leukocytic infiltrate with numerous neutrophils. Which of the following organisms is the most likely cause of this man's infection?

Accepted Answer

Neisseria gonorrhoeae

Answer

Pseudomonas sp

Answer

Escherichia coli

Answer

Mycobacterium tuberculosis

Question 7

Which of the following is the most common cause of subacute endocarditis?

Accepted Answer

Streptococcus viridans

Answer

Staphylococcus epidermidis

Answer

Streptococcus pyogenes

Answer

Staphylococcus aureus

Question 8

True statement about diphtheria toxin is -

Accepted Answer

Toxin is phage mediated

Answer

Toxin acts by inhibiting synthesis of capsule

Answer

Endotoxaemia causes systemic manifestation

Answer

Toxin is required for local infection

Question 9

Which of the following organisms is commonly implicated in spontaneous bacterial peritonitis in patients of Nephrotic syndrome?

Accepted Answer

Streptococcus pneumoniae

Answer

Salmonella

Answer

Hemophilus influenza

Answer

Staphylococcus

Question 10

The most virulent pathogenic Bacillus species is

Accepted Answer

Bacillus anthracis

Answer

Bacillus cereus

Answer

Bacillus subtilis

Answer

Bacillus megaterium

Bacteriology — MCQs

Bacteriology — MCQs

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